Polygons

Question 1

What is a Convex Polygon?

Answer 1

A shape with all interior angles less than 180 degrees

Question 2

What do we call the process of splitting a Concave Polygon into a set of Convex Polygons?

Answer 2

Tessellation

Question 3

What does the Surface Normal of a Polygon allow us to do?

Answer 3

Distinguish the front and back of the Polygon

Describe the orientation of the Polygon

Question 4

How do we find the Surface Normal of a Polygon?

Answer 4

1. Choose a pair of sequential edge vectors, E1 and E2
2. Invert the first edge vector, so both vectors have the same source
3. Calculate their cross product
4. Normalise the vector

Question 5

What is a Polygon Soup?

Answer 5

A way of representing a scene as a giant collection of individual polygons

Question 6

What are the problems with using a Polygon Soup to represent a scene?

Answer 6

1. Huge waste of storage space, vertices are repeated even though they are the same between polygons
2. Loss of semantics, we do not know which polygon belongs to what
3. Interaction with the model is difficult

Question 7

Using a Triangle Strip, how many Vertices are required to represent N Triangles?

Answer 7

N+2

Every time we want to add a triangle to the mesh we only need to add a single vertex

Question 8

Using a Triangle Fan, how many Vertices are required to represent N Triangles?

Answer 8

N+2

Every time we want to add a triangle to the mesh we only need to add a single vertex

Question 9

Using a Quadrilateral Strip, how many Vertices are required to represent N Quadrilaterals?

Answer 9

2N+2